1. Field of the Invention
The invention relates to a method of manufacturing a pipe of metal which is corrugated transversely of its longitudinal direction and receives a corrugation consisting of wave peaks and wave valleys. In the method, an corrugating device is used which impresses a first corrugation as a preliminary corrugation into a pipe which is moved in its longitudinal direction through the corrugating device, with a predetermined axial distance between the wave peaks, wherein the distance between the wave peaks is subsequently reduced by a clamping unit resting against the pipe for obtaining a second corrugation. The invention also relates to a device for carrying out the method. (CH 496 490 A).
2. Description of Related Art
Methods and devices for manufacturing pipes which are corrugated transversely of their longitudinal direction have been known and used for years. Because of the corrugation, the pipes are easily bendable and are stable with respect to radial loads. The corrugation may be helically shaped or ring shaped. This is achieved with appropriate devices by pressing the corrugation into a pipe which is smoothed and is moved, in its longitudinal direction. Such pipes can be utilized for transporting liquid or gaseous media. They may also be utilized as electrical conductors for high frequency cables or as jackets for high voltage cables and news cables. The degree of bendability depends largely on the axial distance between the wave peaks and the depth of the corrugation, i.e. on the radial distance of the wave peaks and the respectively adjacent wave valleys.
DE 24 00 842 A1 describes a method and a device for manufacturing a pipe of high flexibility with an corrugation whose wave peaks rest tightly against each of and which has a relatively deep corrugation. After embossing the corrugation in a corrugating device, the pipe is pressed through a pull out device against a ring shaped tool and thereby is upset as a result, so that the axial distance between the wave peaks is reduced.
The above mentioned CH 496 490 A describes an corrugating device for pipes which includes a first arrangement in which ring shaped notches are discontinuously pressed step by step into a smooth pipe. The pipe provided with a corrugation produced by the notches is fed to a second arrangement in which the axial distance between the wave peaks and the corrugation produced in the first arrangement is reduced. The second arrangement consists of three parts which are connected to one another through springs acting in the axial direction of the pipe. The three parts interact in a two stage manner of operation, compress the corrugation of the corrugated pipe, and effect a forward movement of the pipe by means of the first arrangement by a step. In the first arrangement, another ring shaped notch is pressed into the pipe.